Circulatory mechanism

• The deoxygenated blood collected by the veins accumulates in the sinus venosus, before entering the heart.
• Blood first enters the atrium of the heart, which is a large chamber. Then it enters the ventricle, from where it is pumped into the tube, bulbus arteriosus.
• Through bulbus arteriosus, the blood reaches the aorta and then the gills.
• They facilitate the exchange of gases, i.e. absorption of oxygen from water and elimination of carbon dioxide.
• Then the oxygenated blood is transported throughout the body with the help of blood vessels.
• Blood facilitates the transport of oxygen and nutrients.
• It also collects carbon dioxide which is again transported to the heart and then to the gills, to be removed from the body.